Re: PET 2001 fix Part 3 - RAM/ROM board etc.

From: MikeS <>
Date: Wed, 18 May 2011 10:43:59 -0400
Message-ID: <6E0E7F6D87F04D549E01A1E3F4C28AAA@vl420mt>
----- Original Message ----- 
From: "Baltissen, GJPAA (Ruud)" <>
To: <>
Sent: Wednesday, May 18, 2011 7:05 AM
Subject: RE: PET 2001 fix Part 3 - RAM/ROM board etc.

> Hallo Philip,

>> ... the weird screen repeat thing ...

> I suspect one of the two 74177s at D6/D7. See 320132-3.gif that can be
> found at Bo's site.

Just for the record, I think we're dealing with the 320081 board; same chip
numbers though.

Couldn't hurt, but I think I'd put my money somewhere else; if I understand
it correctly the counters get preloaded with a different bit pattern
(current screen address) at the beginning of every line, so if the timing of
the clear and load pulses is correct it's hard to see what defect would put
them consistently off by 3 and then skip a count.

Am I missing something?

Are you a betting man? ;-)

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Received on 2011-05-18 15:00:03

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